Process for the production of photographic prints.



STATES PATENT OFFICE.

Specification of Letters latent.

Q WILLIAM WILLISpOF BRASTED CHART, KENT, ENGLAND.

PROCESS FOR THE PRODUCTION OF PHOTOGBAIl-IIC PRINTS.

Patent-ed Dec. 8, 1914.

l lo Drawhig. Original application filed September 22, 1913, Serial No. 791.021. 'Dlvfacd and this application "To all whom it may concern:

vented certain new and useful'Improvements in Processes for the Production of Photographic Prints, of which the following is a specification.

This invention consists in improvements in or relating to the production of photographicprints by the use of apaper coated with a sensitive coating of the nature described in my co-pending patent application Serial No. 791021, filed September 22, 1913.

The specification above referred to relates to the production of a photographic printing paper in which thecoatin'g 'or surface sensitive to light contains salts of ,iron, silver and platinum.

The process of making pl'io tographic prints according to the present invention is based on the discovery- I have made that the reduction of silver chlorid by a solution of ferrous oxalate in potassium oxalate is greatly facilitated, increased in rapidity and made more complete, by placing in contact with this silver salt a small quantity of potassium chloro-platinite beforethe reducing agent (ferrous oxalate) is applied to the silver-salt. And I have found that the only salts of platinum of value in thus aiding in the reduction of silver chlorid by ferrous oxalate are salts of chlorin and platinum that is to say ehloro-plntinites or chloroplatinates, salts which are also described as platino-chlorids or platiui-chlorids. And I also find )lntinic chlorid to be of value. The salts of p atinum just named are themselves reducible by a solution of ferrous oxalate and when one of these salts is used as'above described to aid in the reduction of silver chlorid it will be reduced together with the silver salt and both platinum and silver will be liberated. This effect of platinum salts in aiding the reduction of silver chlorid can be easily shown by a purel chemical method but perhaps more readily fy a practical trial on paper in the manner ollowing: If the paper is first of all coated with silver chlorid and then with ferric oxalate, thenex )osed to light'undera negative and then developed on potassium oxalate it yields only a. oor image, but if in addition to the silver ch orid and ferric oxalate thecoating is made .to

filed June 2, 1914. Serial No. 842,388.

contain -a small quantity of potassium chloro-platinite, then on exposure and development a stronger image of blackish color will be obtained; and it has been proved that the intensity of this image is due mostly to thefincreased reduction of the silver salt and only slightly to the reduction of the small quantity of platinum salt used in this experiment.

In a preferred method of manufacture of the printing paper the paper is coated with silvenchlorid which may be applied or attached to the surface as an emulsion in gelatin or other suitable medium, or formed on the surface by the well-known process of double decomposition. The coated surface is then again coated with a solution of ferric oxalate in which is dissolvcd some potassium chloroplatinito (l ,ltCl The coated paper is finally well dried in any suitable way and is then ready for use.

The process for making printsfrom a paper treated in the manner described above is as follows :'.lhe sensitized paper is first of all exposed to light behind a negative or othersuitable screen and then immersed in a developing solution made by dissolving 53 grams of potassium oxalate in 18.12 grams of water. In about one minute development is usually completed. The developed print is then removed to a clearing hath made Unis-potassium bisulfate grams, potassium oxalate 14.2 grams, water 2840 grams. In this bath the paper should remain from ten to fifteen minutes and then it is well washed in several changes of water. Finally the print is fixed in a hypo solution made by dissolving 28.4 grams of sodium hyposulfite in 284 grams of water. The print is finally washed in several changes of water.

Other methods and salts may be used for developing and clearing or fixing the prints, but the method described is an excellent one.

The production of an image on the. paper by exposure to light under a negative and subsequent development in potassium oxalate solution is effected in the following manner :The action of light through the negative forms on the sensitive coating of the paper a faint image consisting mainly of ferrous oxalate. This exposed paper is now immersed in a solution of potassium oxalate which quickly' commences to .dissolve the ierrous oxalate forming the image,

but this solution of ferrous salt in potassiunr is of a black tone agreeable to the eye and does not require toning. The unaltered salts are'then dissolved out from the paper in any suitable way.

r-\ccording to a modification of a process of making photographic prints according to this invention a paper may be employed or in not contained in the developing soployed in which the coating of chloroplatinite or chloro-platinate may be omitted or reduced to a minimum. The paper is exposed in the usual manner and isthereafter treated with a solution of the 'chloro-platinite or chloro-platinate in admixture with the developing solution.

What I claim as my'invention and desire to secure by Letters Patent is 1. Thehe'rein described process of making photographic'prints which consists in "exposing to light behind a-nc ative a paper coated'with a haloid salt of sil i Copies of this patent may be'obtalned for In which the platinum salts may be wholly lutiomflthat is to say, a paper may be em ver and with ferric oxalate and developing the exposed paper in potassium oxalate in the presence of a salt of platinum and chlorin.

.h'lhe herein described process of making photographic prints which consists in exposing to light behind a negative a paper coated with silver chlorid and with lerric oxalate and developing the exposed paperin potassium oxalate in the presence of potassium chlm'o-piatiuite.

3. The herein described process of making photographic prints which consists in exposing to ight behind a negative-apaper coated with silver chlorid and with ferric oxalate, developing the exposed paper in potassium'oxalate in the presence of potassium chloro-platinite and dissolving out the unaltered salts.

-i-. lhe herein described process of making photographic prints which consists in exposing to light behind a negative a paper coated with a haloid salt of silver, a salt of platinum and chlorin and ferric oxalate and developing the exposed paper in potassiunr oxalate.

The herein described process of making photographic prints which consists of'exposing' to light behind a negative a paper coated' wdth silverchlorid, potassium chloro-platini'te and -ferric oxalate developing the exposed paper in potassium oxalate and dissolving out the unaltered salts.

In testimony whereof I have signed my name'to this specification in the presence of two subscribing witnesses.

WILLIAM WILL Witnesses W. H. SMITH, E. A. Sam.

five cents each, by addressing the Commissioner of Patents.

Washington, D. 0." 

